The present invention relates to a paper transport for transporting a paper web past the print station of a printer system and, more particularly, to such a transport for simulating movement of documents past the print station to permit testing and adjustment of a printer system. The paper transport is designed specifically for use with a printer system which senses the presence and the speed of movement of a succession of documents past the print station and which prints information, such as an address, on each of the documents.
Various types of prior art systems have been utilized for addressing preprinted documents, such as magazines, newspapers, catalogs, promotional material, and the like; and such systems have, in general, employed electrostatic printers or other printing devices for printing the addresses on a strip of labels. The printed labels were then applied to the magazines or newspapers by a suitable label application device. A typical prior art device for feeding preprinted documents and applying such labels thereto is disclosed in U.S. Pat. No. 2,606,681, issued Aug. 12, 1952, to Ridenour.
Other types of prior art addressing systems have printed addresses directly on the printed documents. Such a system, including a document feed arrangement, is disclosed in U.S. Pat. No. 4,122,457, issued Oct. 24, 1978, to Erikson et al. The Erikson system includes several ink jet printing nozzles which are oscillated back and forth across a moving document to print lines of characters on the document. Erikson discloses each nozzle printing at least one line of characters, and the suggestion is made that a single nozzle may be utilized to print more than one line. Since the Erikson et al device includes very few nozzles to accomplish printing, the device is limited in the speed at which it can address documents. Additionally, the Erikson et al printer system incorporates its own document transport and, therefore, is not readily compatible with document feed lines at existing printing facilities.
In order to provide an address printing system, capable of operating at high speeds and readily integratable into an existing document feeder system, a portable ink jet printing system, which does not require an electrical interface between the document feeder system and the printer, has been developed and is disclosed and claimed in U.S. patent application Ser. No. 142,787, filed Apr. 22, 1980, by Bok et al now U.S. Pat. No. 4,283,731, and assigned to the assignee of the present invention. The Bok et al device includes an ink jet print head which is supported by a printing arm movably mounted on a portable control console. The control console is adapted for placement adjacent a document feeder, which may be any one of a number of known feeder devices such as are typically incorporated in an existing printing facility. The printing arm is mounted on the control console in such a manner that it extends into a printing position over the feeder when the control console is placed adjacent thereto. The printing arm may be moved into a storage position which is clear of the document feeder when printing has been completed.
The Bok et al printer prints directly upon the face of documents transported past a print station, beneath the printing arm, and therefore eliminates the need for application of address labels. Thus, compatibility with existing addressing systems is achieved by merely removing the label applicator which previously was utilized with the document feed system. The print arm may thus occupy the space which previously had been occupied by the label applicator.
In order to provide compatibility with a broad range of existing document feeders, without the need for electrical interface circuitry connecting the printer system with the feeders, the Bok et al system includes a document sensor which is mounted on the printing arm and which senses the movement of a document past the print station. This sensor is of the photo-optical type which directs a light beam downward into the path of the documents. The light beam is thereafter reflected upward to the sensor, either by a document moving past the print station or by the document support platen of the feeder. Typically, the feeder support platen is highly reflective and, therefore, a greater amount of light is reflected to the sensor by the platen than by the documents, which are of lower reflectivity. The sensor thus provides a means for detecting the movement of the leading edge of each document past the print station beneath the printer so that the printed address may be positioned appropriately with respect to this leading edge.
It will be appreciated that the speed of movement of the documents past the print station may vary somewhat during operation of a document feeder and, further, that the speed of movement of documents will vary somewhat more widely between different types of feeder devices. In order to synchronize the deposit of drops on the document surfaces with the movement of the documents past the print station in order that the drops may be deposited in a precisely controlled manner to form the desired characters of the address, the Bok et al printer system includes a tachometer wheel, mounted on the print arm, which is connected to a tachometer. The tachometer wheel contacts each of the documents moving past the print station. The tachometer provides a tachometer pulse train, the frequency of which is proportional to the speed of document movement.
The Bok et al printer system is designed specifically for sensing the presence and speed of movement of a succession of documents transported past a print station, and for printing an address or other information on each of the documents. When it is necessary to service or adjust the Bok et al printer system, it is desirable to observe the printer as it prints upon a continuous web of paper, which may thereafter be disposed at little expense. However, such a web would not provide the fluctuations in reflectivity which the document sensor of the Bok et al printer system utilizes to determine the proper location for printing addresses on each of the documents. Thus, it is seen that there is a need for a printer test unit which simulates the movement of a plurality of documents past the print station as it transports a paper web beneath the printing arm for printing thereon.
Additionally, since print image quality produced by the Bok et al printer system is dependent, in part, upon the document feeder system, it is desirable to provide a paper transport which may be used in conjunction with the Bok et al printer system to assess print image quality. Further, a paper transport which simulates the movement of documents past the print station permits proofing of address information which is to be printed by the Bok et al printer system on a number of documents.